US3681199A - Process of producing yeast of low plasticity and high solids content - Google Patents

Process of producing yeast of low plasticity and high solids content Download PDF

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Publication number
US3681199A
US3681199A US21977*[A US3681199DA US3681199A US 3681199 A US3681199 A US 3681199A US 3681199D A US3681199D A US 3681199DA US 3681199 A US3681199 A US 3681199A
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yeast
plasticity
urea
glycerol
filtered
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Karl Rokitansky
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Patentauswertung Vogelbusch GmbH
Vogelbusch GmbH
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Vogelbusch GmbH
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N1/00—Microorganisms, e.g. protozoa; Compositions thereof; Processes of propagating, maintaining or preserving microorganisms or compositions thereof; Processes of preparing or isolating a composition containing a microorganism; Culture media therefor
    • C12N1/04—Preserving or maintaining viable microorganisms

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  • FIG. 1 A first figure.
  • FIG. 2B 8 F/asfic/afy Sham Time G(yaera/ A0170)? FIG. 2B
  • FIG. 3A PROCESS OF PRODUCING YEAST 0F LOW PLASTICITY AND HIGH SOLIDS CONTENT 5 Sheets S'heet 5 Filed April 1, 1970 /Iorf 77'me Sodium Chloride Acfion
  • FIG. 3A PROCESS OF PRODUCING YEAST 0F LOW PLASTICITY AND HIGH SOLIDS CONTENT 5 Sheets S'heet 5 Filed April 1, 1970 /Iorf 77'me Sodium Chloride Acfion
  • the present invention relates to a process of producing yeast and more particularly to a process of producing yeast of low plasticity and increased dry solid content.
  • the suspension of the thus cytorrhyzed cells is applied to a suction filter, preferably a rotary drum suction filter.
  • the osmotically active compound which is present in the extracellular water remains in the filter cake. Its amount depends on the pressure difference applied to the suction filter.
  • a suction filter preferably a rotary drum suction filter.
  • the osmotically active compound which is present in the extracellular water remains in the filter cake. Its amount depends on the pressure difference applied to the suction filter.
  • Pat. No. 2,947,668 it is displaced in the layer of the cytorrhyzed cells formed on the filter by a liquid of lower osmotic pressure, preferably by water. Said displacement of extracellular water containing the osmotically active compounds, i.e.
  • washing of the filter cake on the filter is elfected in such a manner that displacement or washing is discontinued before complete reabsorption of the displacing water by the cells in the form of intracellular water takes place.
  • the layer of cell material freed by such washing from the osmotically active compounds is further exposed to the action of the difference in pressure prevailing on the suction filter.
  • the extracellular water content decreases below the value corresponding to and attainable by said dilference in pressure because it is partly reabsorbed by the cells and thus enters the cells as intracellular water.
  • extracellular water as used in said patent and hereinafter in the present specification and claims defines the amount of water in yeast and other cell material which is present outside the cells.
  • said extracellular water is the water or, respectively, the dilute wort solution wherein the yeast cells swim.
  • said extracellular water is that amount of water which is present in the narrow capillary interstices formed by the more or less tightly accumbent cells.
  • intracellular water as used in said patent and hereinafter in the present specification and claims defines the amount of water which is present within the cells themselves.
  • the amount of intracellular water can be varied as explained hereinbefore by subjecting the cells, for instance, the yeast cells to the action of osmotically active compounds.
  • the total water content of the cell material such as yeast is the sum of extracellular water and intracellular water.
  • mashing of the yeast treated with an osmotically active compound is an essential feature in producing a yeast of a high solid content and a low plasticity.
  • 'Ihe washing step requires a considerably increased filter area, i.e. the output of filtered yeast per unit of filter area is considerably reduced when producing a yeast of a high solid content and a low plasticity according to Kuestler et al.
  • Another object of the present invention is to provide a novel and valuable dry yeast product of a high dry solid content, of low plasticity, of improved stability and storability, of better leavening power and baking strength than heretofore possible, said product having other valuable properties distinguishing the same over the products obtained according to said US Patent No. 2,947,668.
  • the process which yields yeast of increased dry solid content, low plasticity, and high stability consists in principle in proceeding as described by Kuestler et al. in Patent No. 2,947,668, namely in admixing to a yeast suspension an osmotically active compound, allowing said compound to act on the yeast, and filtering or centrifuging the cytorrhyzed yeast cells to remove therefrom exuded intracellular water and excess extracellular water. It differs, however, from said Kuestler et al. process by the following features:
  • the extracellular water content and thus the plasticity of the yeast is considerably reduced while its dry solid content remains substantially unchanged.
  • the filtered yeast must be stored according to the present invention for at least 4 hours and preferably 24 hours because that much time is at least required to substantially complete reabsorption of the extracellular water.
  • the process according to the present invention consists in adding specific osmotically active compounds, namely urea or glycerol, to the yeast suspension and especially to yeast cream.
  • Said compounds are capable of being adsorbed by the yeast cells and do 4 not cause significant fermentation.
  • shrunken yeast cells are obtained.
  • the extracellular water and exuded intracellular water are removed to a considerable extent by means of any conventional separating device such as filter presses, centrifuges, or suction filters.
  • the resulting filtered cytorrhyzed yeast which is free of excess extracellular water and part of the intracellular water is then further exposed for a prolonged period of time, i.e., for at least 4 hours to the action of the remaining extracellular water still containing said specific osmotically active compound.
  • a cytorrhyzed yeast material When using other osmotically active compounds than urea or glycerol, a cytorrhyzed yeast material is obtained the cells of which retain their shrunken condition and do not re-absorb extracellular water on storage. Thereby, the extent of the cell shrinkage depends on the concentration of the osmotically active compound remaining in the extracellular water which is not removed by filtration or the like. In contrast thereto, when using urea or glycerol there is also obtained a cytorrhyzed yeast cell material immediately after removal of the cell material from the separating device, for instance, the suction filter.
  • the degree of shrinkage in this cytorrhyzed yeast cell material depends primarily upon the concentration of the specific, osmotically active compound which remains in the residual extracellular water.
  • this shrunken state of the cytorrhyzed yeast cell material changes during storage following the separation step due to the fact that the cells re-absorb at least part of the specific osmotically active compound present in the remaining extracellular water.
  • the specific, osmotically active compounds urea or glycerol By absorption of the specific, osmotically active compounds urea or glycerol by the yeast cells, the osmotic conditions within the cells are changed considerably.
  • the yeast cells exhibit an increasing osmotic pressure in their interior.
  • the osmotic pressure of the extracellular water decreases due to the decreasing content of the specific, osmotically active compound present therein.
  • extracellular water also diffuses into the yeast cells, the extent of diffusion being proportional to the amount of specific, osmotically active compound absorbed therefrom.
  • Due thereto the intracellular water content of the yeast cell material after removal from the separating device and storage for at least 4 hours increases and its extracellular water content decreases. This results in a considerable reduction in plasticity of the yeast cell material.
  • a product of the desired low degree of plasticity is obtained.
  • the extracellular water is transformed into intracellular water, so that the total water content of the yeast cell cake after filtration remains unchanged and the dry solid content of the treated material remains the same as in the material formed on the filter depending on the vacuum or the pressure applied thereto.
  • the process of the present invention is based on the action of the specific osmotically active compounds urea or glycerol upon the filtered yeast cell material and on the separation of the osmotically active extracellular water from the cytorrhyzed yeast cells depending on the separating force (vacuum filtration, centrifugal power) of the separating device as described in the above mentioned US. Patent No. 2,947,668. It differs therefrom, however, as stated hereinabove.
  • the yeast to be treated according to the present invention may be a yeast suspension and especially yeast cream.
  • osmitically active compounds which can be used in this process are urea or glycerol.
  • osmotically active compounds are readily water-soluble and substantially non-toxic, colorless, and odorless. They do not react with the yeast cell components and the cell membrane. They do not cause any substantially fermentation on contact with the yeast. They do not cause foaming and their solutions do not have the tendency to foam. On contact therewith yeast cream does not exhibit budding and, if at all, only a slight increase in gas formation.
  • a short period of time designating the duration of the action of urea or glycerol
  • the time interval which is required for the osmotically active compound added to the extracellular water to cause effusion of intracellular water from the yeast cells and to yield cytorrhyzed, i.e. shrunken yeast cells. This period of time must not be exceeded substantially.
  • absorption of said compounds by the yeast cells takes place simultaneously with cytorrhysis of the cells-although at a relatively slower rate.
  • the yeast cell material for instance, the yeast cell suspension with urea or glycerol only for a short period of time or, respectively, immediately before separation of the removable portion of the extracellular water.
  • the time interval between addition of urea or glycerol to the yeast cell material and its filtration is between about seconds and about 2 minutes, preferably between 210 seconds and 1 minute.
  • urea or glycerol it is preferred, according to the present invention, to add between about 0.1% and about 5.0%, by weight, preferably between about 0.3% and about 2.0%, by weight, of urea or glycerol to 100 l. of the yeast cell suspension, for instance, of yeast cream. 'Of course, as explained above, larger or smaller amounts may also be added to achieve the same desired results. The smallest possible amount of urea or glycerol to achieve a predetermined desired effect will be required when using, as
  • yeast suspensions for instance, yeast cream of as high a cell concentration as possible and of a low content of extracellular water removable, for instance, by filtration at a pressure of 700 mm. Hg. Urea is preferably used in its solid form. However, it is also possible to use more or less concentrated urea solutions.
  • the yeast cell material after removal of a portion of the extracellular water by suction filtration or by centrifuging is exposed according to the present invention to the action of the remaining extracellular water containing residual urea or glycerol, by eliminating the washing step of the process of UJS. Patent No. 2,947,668 after the treatment with said specific, osmotically active compound.
  • the resulting viable yeast cell material obtained according to the process of the present invention differs from an untreated yeast cell material neither in its color, nor in its odor.
  • the taste of the obtained yeast cell material is not unpleasantly altered. When using urea there may arise a slightly cool and strong taste, whilst when using glycerol the taste may be slightly sweet.
  • This process is of special value in the manufacture of packaged small yeast bricks in which the yeast undergoes further drying as well as in the manufacture of yeast to be shipped under difficult climatic conditions.
  • the process according to the present invention has the further important advantage that the yeast output per hour is considerably increased because that part of the surface of the rotary filter which heretofore was required for washing and displacing the extracellular liquid in the tfilter cake can now additionally be used as suction zone for filtering the cytorrhyzed yeast. As a result thereof a thicker yeast layer may be allowed to deposit on the filter and, thus, the filtering capacity per hour is considerably increased.
  • This increase in output over the Kuestler et al. process which includes the Washing step amounts to between 30% and 40%. For instance, while when following the Kuestler et al. process 2200 kg, of yeast are produced on an '8 sq. m. rotary filter, the output amounts to 3000 kg. when proceeding according to the present invention, using urea or glycerol as osmotically active agents, filtering the treated yeast immediately after cytorrhysis is completed, and storing the filtered yeast.
  • the curve in FIG. 1a represents the change in plasticity of unwashed yeast 24 hours after filtration whereby the yeast cream was treated according to the present invention for a short time (2 minutes) only with various amounts of urea before the treated yeast cream was "filtered
  • the curve illustrated in FIG. 1b represents the change in plasticity of unwashed filtered yeast obtained in the same manner whereby, however, various amounts of urea are allowed to react with the yeast for 24 hours before filtration.
  • the curve illustrated in FIG. 211 represents the change in plasticity of unwashed filtered yeast obtained by short time action of glycerol
  • the curve in FIG. 2b represents the change in plasticity by long time action of glycerol.
  • FIG. 3a represents the change in plasticity of unwashed filtered yeast obtained by short time action of sodium chloride and the curve in FIG. 3b represents the change in plasticity by long time action of sodium chloride.
  • the curves in FIG. 4 illustrate the reduction in plasticity of yeast treated with urea according to the present invention and the curves in FIG. illustrate the reduction in plasticity of yeast treated with glycerol according to the present invention.
  • FIGS. la, .1b, 2a, 2b, 3a, and 3b the ordinate indicates the depth of penetration in mm. of a standard indentator weight into the yeast bricks which were shaped under the same conditions, whereby a conventional plasticity measuring apparatus was used.
  • the abscissa in these figures indicates the amount in kg. of the osmotically active agent added to 100 1. of a yeast cream with about 18% of yeast solids.
  • the ordinate also indicates the depth of penetration in mm. while the abscissa indicates the time in hours after completion of the filtration and brick formation.
  • EXAMPLE 1 6 portions of 100 1. each of yeast cream are separated from a sample of 5,000 l. of yeast cream, containing yeast of like characteristics.
  • the first portion is immediately brought on a vacuum rotary drum without pretreatment with urea and is filtered under a pressure of 700 mm. Hg without washing the yeast on the filter.
  • the filtered yeast is removed from the filter and yeast bricks of one half kg. each are formed.
  • the second portion of 100 l. of yeast cream is mixed with 0.1 kg. of urea and is filtered about one minute after urea addition in the same manner as given above in connection with the not pretreated portion of yeast cream.
  • the filtered yeast removed from the filter is also shaped to yeast bricks of one half kg. each.
  • urea to the remaining third to sixth portions of yeast cream are, respectively, 0.5 kg., 1.0 kg., 2.0 kg., or 5.0 kg. per 100 l. of yeast cream.
  • the plasticity of said yeast is determined by means of a conventional plasticity measuring apparatus by measuring, after a period of 24 hours, the depth of penetration of a standard indentator weight into yeast bricks shaped and molded under the same conditions.
  • EXAMPLE 2 6 portions of yeast cream (100 1. each) are processed as given in Example 1 with the modification that, instead of the mentioned amounts of urea, there is added glycerol to the yeast cream portions No. 2 to 6 in amounts of 0.15, 0.75, 1.53, 3.06 or 7.65 kg., respectively. The yeast portions were filtered about one minute after addition of the glycerol. The results are given in Table II.
  • the amounts of glycerol added to each portion of yeast cream are equivalent in respect to molecular weight and to osmotical efiiciency, compared with the amounts of urea in Example 1.
  • EXAMPLE 3 The following comparative tests were carried out with a yeast cream containing about 18 kg. of yeast solids per 1001. of yeast cream.
  • Test group (a) (l) 3 portions of yeast cream were mixed with various amounts of urea and were filtered two minutes after ad dition of the urea on a vacuum rotary drum under a pressure of 700 mm. Hg. The unwashed filtered yeast was removed from the filter drum and yeast bricks of 0.5 kg. were formed.
  • yeast cream 1 portion was filtered. Yeast bricks were formed and their dry solids content and plasticity were determined after storing for 24 hours.
  • Test group (b) (1) 3 portions of yeast cream were mixed with varying amounts of urea. The mixture was kept for 24 hours and was then filtered and the unwashed filtered yeast was treated and tested as described under (a) (1).
  • Test group (1) Amounts added in Dry Mm. decrease Dry Mm. decrease kg./100 l. solids Plasticity of penetration solids Plasticity of penetration yeast content, in mm. (decrease in content, in mm. (decrease in cream percent penetration plasticity) percent penetration plasticity) It is evident from these tests that only when (a) using urea or glycerol as osmotically active agent, (b) filtering the cream shortly, i.e. 2 minutes after admixture of said agent, and (c) allowing the unwashed filtered yeast to stand for 24 hours, the plasticity is considerably reduced while the dry solids content is substantially the same. Test group (b) shows that immediate filtration is an essential feature of the present invention.
  • sodium chloride when subjected to the process according to the present invention does not produce a reduction in plasticity but even a slight increase.
  • FIGS. 1a, 1b, 2a, 2b, 3a, and 3b show more clearly the surprising efiect of the process according to the present invention.
  • lF IG Illustrates the reduction in plasticity caused by the addition of urea and allowing it to act for a short period of time on the yeast cream before filtration
  • FIG. Ib illustrates that the plasticity remains substantially unchanged when allowing urea to act, before filtration, for 24 hours on the yeast cream, and is rather high.
  • FIG. IIa illustrates the plasticity values observed on short time action of glycerol on the yeast cream before filtration, while FIG.
  • FIG. IIb illustrates the plasticity values observed on long time (24 hours) action of glycerol on the yeast cream before filtration.
  • FIG. HIa illustrates the plasticity values observed on short time action of sodium chloride on the yeast cream before filtration
  • FIG. I'IIb the plasticity values on long time (24 hours) action of sodium chloride on the yeast cream before filtration.
  • EXAMPLE 4 The following tests were carried out in order to prove that not only short time action of glycerol or urea on the yeast cream before filtration is an essential feature of the present invention as this is shown in Example 3 and FIGS. Ia to IlIb, but also that the filtered, unwashed, treated yeast must be stored after filtration for at least 4 hours in order to effect re-absorption of extracellular water into the cytorrhyzed yeast cells. -If the yeast is not stored for a prolonged period of time, but is used within about 3 hours after filtration, the plasticity is not reduced to the optimum extent.
  • glycerol yeast is slightly superior to the urea yeast. No difference in taste could be found yeast cream Pl t1 it d t d between the control and the glycerol yeast while the urea as c y e yeast tasted slightly stronger but not at all disagreeable. knmediatelyf naiter filtration 6.3 6.3 6.3 It may be mentioned that glycerol and urea in the cona ter tmmn- 475 5 7 centrations present in the unwashed filtered yeast are 1 1. 2 harmless and not objectionable in nitritional-physiological e105 1: 7 '1. 1 respect- 2. 95 1.65 1. 05 10 EXAMPLE 6 2. 95 1. e5 1. 05
  • IV for a period of time between about 5 seconds and and V clearly illustrate the decrease in plasticity of the about 2 minutes to cause exudation of intracellular filtered but unwashed yeast on storing and the storage time water from and cytorrhysis of the yeast cells; at which no further decrease in plasticity is observed.
  • Leaveningtime 3 The process according to claim 1, wherein the os- Test No. Sample 1st test 2d test 3d test Total to relanvely small $111112: iiilft'rasiiddr i3 33 3% it? F amrding claim wherein the Yeast of yeast cream. suspension 1s yeast cream. 3 5.8 kg. of glycerol/100 44 27 25 96 l. of yeast cream.
  • filtered yeast according to the present invention show by weight, to 1001. of yeast suspension.

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AT856364A AT260842B (de) 1964-10-07 1964-10-07 Verfahren zur Gewinnung von Hefe od. ähnl. pflanzlichem Zellmaterial mit erhöhtem Trockensubstanzgehalt

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USB498208I5 (de) * 1974-08-16 1976-04-13
US4318991A (en) * 1978-03-11 1982-03-09 Henkel Kommanditgesellschaft Auf Aktien (Henkel Kgaa) Baker's yeast with improved leavening power in acid dough
WO1983000277A1 (en) * 1981-07-27 1983-02-03 Nabisco Brands Inc Compressed yeast product and process
US5288632A (en) * 1986-04-12 1994-02-22 Ad2 Limited Encapsulation of material in microbial cells

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2614348C3 (de) * 1976-04-01 1986-01-02 Versuchsanstalt Der Hefeindustrie E.V., 1000 Berlin Pulverförmiges, freifließendes Frischbackhefepräparat

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USB498208I5 (de) * 1974-08-16 1976-04-13
US4001480A (en) * 1974-08-16 1977-01-04 Swift & Company Encapsulation process utilizing microorganisms and products produced thereby
US4318991A (en) * 1978-03-11 1982-03-09 Henkel Kommanditgesellschaft Auf Aktien (Henkel Kgaa) Baker's yeast with improved leavening power in acid dough
WO1983000277A1 (en) * 1981-07-27 1983-02-03 Nabisco Brands Inc Compressed yeast product and process
US4405650A (en) * 1981-07-27 1983-09-20 Nabisco Brands, Inc. Compressed yeast product and process
US5288632A (en) * 1986-04-12 1994-02-22 Ad2 Limited Encapsulation of material in microbial cells

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AT260842B (de) 1968-03-25
DE1442142A1 (de) 1968-11-21
DE1442142C3 (de) 1973-09-27

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